Modular uniplanar pedicle screw assembly for use with a polyaxial bone fastener

ABSTRACT

A modular uniplanar pedicle screw assembly for use with a polyaxial bone fastener. The modular assembly comprises a uniplanar tulip assembly adapted to be coupled to a head of the polyaxial bone fastener, wherein the uniplanar tulip assembly includes a longitudinal slot. The modular assembly further includes an adapter having a lower portion and an upper portion. The lower portion is sized and shaped to be received in a recess of the bone fastener head. The upper portion extends from the lower portion and is adapted to slide along the longitudinal slot of the uniplanar tulip assembly to allow movement of the uniplanar tulip assembly in a first plane along a direction that is parallel to a longitudinal axis of the longitudinal slot, the longitudinal slot preventing movement of the uniplanar tulip assembly in a second plane lateral to the first plane relative to the bone fastener.

FIELD OF THE INVENTION

The present invention relates generally to a pedicle screw assembly, andmore particularly to a uniplanar tulip assembly that can beintra-operatively coupled to a polyaxial bone fastener.

BACKGROUND OF THE INVENTION

Many types of spinal irregularities such as scoliosis, kyphosis,lordosis, etc., can cause pain, limit range of motion, or injure thenervous system within the spinal column. These irregularities can resultfrom trauma, tumor, disc degeneration, and disease. Oftentimes, theseirregularities are treated by adjusting a portion of the spinal columnand immobilizing that portion of the spine. This treatment involvesaffixing a plurality of pedicle screw assemblies (which includes a tulipelement and a bone fastener) to one or more vertebrae and thenconnecting the pedicle screw assemblies to an elongate rod thatgenerally extend in the direction of the axis of the spine. Theconnection is typically achieved by attaching the elongated rod to thetulip element of each pedicle screw assembly affixed to the vertebras.

There are many types of pedicle screw assemblies that surgeons can useto immobilize a portion of the spinal column. Such assemblies include,for example, polyaxial, monoaxial, and uniplanar pedicle screwassemblies. Each of these assemblies is characterized by whether theirtulip element can be angulated relative to the bone fastener and inwhich plane(s) of the bone fastener.

A polyaxial pedicle screw assembly provides the greatest flexibility intulip movement. More specifically, a tulip element of a polyaxialassembly is allowed to pivot freely in any direction and in all planesrelative to a central axis of its respective bone fastener. This featureenables polyaxial assemblies more variability in rod placement.

A monoaxial pedicle screw assembly typically has a unitary constructionin that the bone fastener and tulip element are machined from a singlepiece of biocompatible metal or plastic. This type of constructionprevents the monoaxial pedicle screw assembly from being able to pivotabout the bone fastener. This type of unitary construction alsodisallows the tulip element from being uncoupled from the bone fastener.

A uniplanar pedicle screw assembly, on the other hand, allows its tulipelement to pivot back and forth in one plane about a central axis of thebone fastener, while simultaneously preventing movement of the tulipelement in all other planes. This feature enables uniplanar assembliesto maintain rigidity in a particular plane during deformity correction.It should be noted, however, that uniplanar assemblies share a commonproperty with monoaxial assemblies; that is, the tulip element of auniplanar assembly cannot be uncoupled from the bone fastener andrequires a different bone fastener head geometry to provide rigidity.This is due to the fact that the bone fastener head of a uniplanarassembly has a geometry that is different from the bone fastener head ofa polyaxial assembly. The geometry for a uniplanar assembly is designedto resist angulation in one direction, but it also requires a morecomplex assembly process that is time consuming and dangerous in-situ.

With this knowledge, surgeons performing surgery to correct spinalirregularities will typically decide beforehand on which of the pediclescrew assemblies to affix to a pedicle of a particular vertebra. Forexample, a surgeon may decide beforehand to use a polyaxial pediclescrew assembly on a particular vertebral body for ease of rod placement.Based on this decision, the surgeon will affix the polyaxial assembly(which includes a tulip element and a bone fastener) as a single unitonto that vertebral body. However, after affixing the polyaxial assemblyonto the vertebral body, the surgeon may determine intra-operativelythat deformity correction is needed at the affected vertebral body andthat a uniplanar assembly would be more suitable for this purpose.

One way to solve this problem is to replace (e.g., by unscrewing) thepolyaxial assembly initially affixed to the vertebral body, and thenaffixing (e.g., by screwing) a uniplanar assembly into the same hole.However, this solution is time consuming because it requires multiplesteps and may compromise the structural integrity of thepedicle/vertebra due to the repeated screwing and unscrewing of bonefasteners.

Because of these deficiencies in the prior art, there exists a need toprovide a modular pedicle screw assembly that enables a surgeon tointra-operatively use different types of tulip assemblies without havingto screw and unscrew bone fasteners.

SUMMARY OF THE INVENTION

The present invention provides a way to couple a uniplanar tulipassembly onto the same bone fastener head as a polyaxial tulip assemblywithout some of the deficiencies in the prior art.

In accordance with an illustrative embodiment of the present invention,provided is a modular pedicle screw assembly that allows a surgeon toinstall, couple, etc., a uniplanar tulip assembly onto the same bonefastener as a polyaxial tulip assembly. The uniplanar tulip assembly ofthe present invention comprises a longitudinal slot and an adapterarranged with a lower portion and an upper portion. The lower portion ofthe adapter is sized and shaped to be received in a recess arranged onthe head of a polyaxial bone fastener. The upper portion (which extendsfrom the lower portion) is adapted to slide along the longitudinal slotof the uniplanar tulip assembly; particularly, the longitudinal slot ofthe saddle element of the tulip assembly. This configuration: (i) allowsmovement of the tulip assembly in a first plane along a direction thatis parallel to a longitudinal axis of the longitudinal slot and (ii)prevents movement of the tulip assembly in a second plane lateral to thefirst plane relative to the bone fastener. In this way, a surgeon canintra-operatively choose between a polyaxial tulip assembly and auniplanar tulip assembly without having to screw and unscrew the bonefastener from the vertebral body, as currently performed in the priorart.

In an alternative embodiment of the present invention, provided is atulip assembly that is adapted to constrain the polyaxial movement ofthe overall assembly to a uniplanar movement. The tulip assemblycomprises a tulip element, a saddle element, and a clamp element. Thesaddle element rigidly houses the clamp element to form a locking clampassembly, which assembly is arranged within a bore of the tulip element.The clamp element is adapted to be coupled onto the head of a bonefastener in such a way that the tulip assembly is allowed to pivotfreely in all directions about a central axis of the bone fastener head.When the clamp element is compressed within the saddle element, thetulip assembly is no longer permitted to pivot freely. That is, thepolyaxial movement of the tulip assembly is constrained to a uniplanarmovement even though the clamp element has been compressed within thesaddle element. This is due to the fact that the saddle element has twoprotrusions, each of which is seated within a corresponding recess(e.g., a keyhole) arranged on an inner surface of the tulip element.This configuration enables the tulip element to pivot or angulate in afirst plane, while providing rigidity in a second plane lateral to thefirst plane.

In a further alternative embodiment of the present invention, the tulipelement is coupled to a sleeve assembly that has a pair of oppositelypositioned inwardly protruding pins. The pins of the sleeve assembly isadapted to prevent movement of the tulip element from pivoting about acentral axis of bone fastener in a first plane, while providing rigidityin a second plane lateral to the first plane.

In a further embodiment of the present invention, the tulip element andbone fastener head are adapted to receive a translation rod to providethe tulip element with rotational and translational capabilitiesrelative to the bone fastener.

These advantages of the present invention will be apparent from thefollowing disclosure and the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a polyaxial pedicle screw assembly inaccordance with an illustrative embodiment of the present invention.

FIG. 2 is a perspective view of a locking clamp assembly for thepolyaxial pedicle screw of FIG. 1 in accordance with the presentinvention.

FIG. 3 is a cross-sectional view of the locking clamp assembly of FIG. 2in accordance with the present invention.

FIG. 4 is a top view of a saddle element for the polyaxial pedicle screwof FIG. 1 in accordance with the present invention.

FIG. 5 is a side view of the saddle element of FIG. 4 in accordance withthe present invention.

FIG. 6 is a cross-sectional view of the locking clamp assembly of FIG. 2disposed in a tulip element in an unlocked configuration in accordancewith the present invention.

FIG. 7 is a cross-sectional view of the locking clamp assembly of FIG. 2disposed in a tulip element in a locked configuration in accordance withthe present invention.

FIG. 8 is a top view of a tulip element depicted in FIGS. 6 and 7 inaccordance with the present invention.

FIG. 9 is a top view of a locking cap assembly in accordance with thepresent invention.

FIG. 10 is a perspective view of the locking cap assembly depicted inFIG. 9 in accordance with the present invention.

FIG. 11 is a cross-sectional view of the locking cap assembly of FIG. 10in accordance with the present invention.

FIGS. 12-14 is a cross-sectional view of the polyaxial pedicle screwassembly of FIG. 1 in accordance with the present invention.

FIG. 15 is a perspective view of a modular uniplanar pedicle screwassembly having a uniplanar tulip assembly and adapter in accordancewith the present invention.

FIG. 16 is a perspective view of installing the modular uniplanarpedicle screw assembly of FIG. 15 onto the bone fastener head of thepolyaxial pedicle screw assembly of FIG. 1 in accordance with thepresent invention.

FIG. 17A is a cross-sectional front view of the adapter inserted intothe recess of the bone fastener and the longitudinal slot of the saddleelement in accordance with the present invention.

FIG. 17B is a cross-sectional side view of the adapter inserted into therecess of the bone fastener and the longitudinal slot of the saddleelement in accordance with the present invention.

FIG. 17C is a cross-sectional side view of the adapter sliding along thelongitudinal slot of the saddle element in accordance with the presentinvention.

FIGS. 18A-18D is a cross-sectional view of an insertion tool forinserting the adapter in accordance with the present invention.

FIG. 19A is a perspective view of a modular uniplanar tulip assembly inaccordance with an alternative embodiment of the present invention.

FIG. 19B is a cross-sectional side view of the modular uniplanar tulipassembly of FIG. 19A in accordance with an alternative embodiment of thepresent invention.

FIG. 19C is a cross-sectional front view of the modular uniplanar tulipassembly of FIG. 19A in accordance with an alternative embodiment of thepresent invention.

FIG. 20 is a perspective view of the tulip, saddle, and clamp elementsof the modular uniplanar tulip assembly of FIGS. 19A-19C in accordancewith an alternative embodiment of the present invention.

FIG. 21 is a perspective view of pedicle screw coupled to a sleeveassembly for converting the pedicle screw to a uniplanar pedicle screwin accordance with an alternative embodiment of the present invention.

FIG. 22 is a perspective view of a tulip element having one or moreslots for receiving an insert of a sleeve assembly in accordance with analternative embodiment of the present invention.

FIG. 23 is a top view of the sleeve assembly of FIG. 21 in accordancewith an alternative embodiment of the present invention.

FIG. 24A is a perspective view of a pedicle screw assembly with atranslation rod in accordance with an alternative embodiment of thepresent invention.

FIG. 24B is a perspective view of the pedicle screw assembly of FIG. 24Bdisassembled in accordance with an alternative embodiment of the presentinvention.

FIG. 25A is a front view of the pedicle screw assembly of FIG. 24A inaccordance with an alternative embodiment of the present invention.

FIG. 25B is a cross-sectional front view of the pedicle screw assemblyof FIG. 25A in accordance with an alternative embodiment of the presentinvention.

FIG. 26A is a side view of the pedicle screw assembly of FIG. 24Ashowing rotational movement of the tulip element relative to the bonefaster in accordance with an alternative embodiment of the presentinvention.

FIG. 26B is a cross-sectional side view of the pedicle screw assembly ofFIG. 26A showing rotational movement of the tulip element relative tothe bone faster in accordance with an alternative embodiment of thepresent invention.

FIG. 27A is a top view of the pedicle screw assembly of FIG. 24A showingtranslational movement of the tulip element relative to the bone fasterin accordance with an alternative embodiment of the present invention.

FIG. 27B is a front view of the pedicle screw assembly of FIG. 27Ashowing translational movement of the tulip element relative to the bonefaster in accordance with an alternative embodiment of the presentinvention.

FIG. 28 is a cross-sectional view of the pedicle screw assembly of FIG.24A with a fusion rod and a locking cap assembly in accordance with analternative embodiment of the present invention.

DETAILED DESCRIPTION

A Modular Uniplanar Pedicle Screw Assembly for Use with a Polyaxial BoneFastener

FIG. 1 is an exploded view of a polyaxial pedicle screw assembly 2 inaccordance with an illustrative embodiment of the present invention. Asillustrated, the polyaxial pedicle screw assembly 2 may comprise apolyaxial bone fastener 4, a polyaxial tulip assembly 101 having a tulipelement 10 and a locking clamp assembly 6 (which may comprise, forexample, a clamp element 7 and a saddle element 8), and a locking capassembly 12. As will be discussed in more detail below, the bonefastener 4 may be loaded from the bottom of the tulip element 10 withthe locking clamp assembly 6 already loaded therein. Prior to beinglocked into place, the tulip element 10 can be pivoted, angulated, androtated in a plurality of positions with respect to a central axis ofthe bone fastener 4. Once the tulip element 10 is at the desiredposition with respect to the bone fastener 4, the tulip element 10 maybe locked onto the bone fastener 4. In the illustrated embodiment, thelocking cap assembly 12 is configured to secure a rod 14 in the tulipelement 10. In one embodiment, the tulip element 10 is fixed onto thebone fastener 4 contemporaneously with securing of the rod 14 in thetulip element 10.

As illustrated by FIG. 1, the bone fastener 4 includes a head 16 and ashaft 18 that extends from the head 16. The illustrated embodiment showsthe shaft 18 having a tapered shape and threads 20. Those of ordinaryskill in the art will appreciate that the shaft 18 may have a number ofdifferent features, such as thread pitch, shaft diameter to threaddiameter, overall shaft shape, and the like, depending, for example, onthe particular application. While the head 16 may have any generalshape, at least a portion of the head 16 may have a curved surface inorder to allow for rotational movement or angular adjustment of the bonefastener 4 with respect to the tulip element 10. For example, at least aportion of the head 16 may be shaped to form a portion of a ball or atleast a portion of a sphere. As illustrated, the head 16 may have aroughened or textured surface 22 that improves engagement with the clampelement 7. In certain embodiments, the head 16 may have a toolengagement surface, for example, that can be engaged by a screw-drivingtool or other device. The tool engagement surface can permit thephysician to apply torsional or axial forces to the bone fastener 4 todrive the bone fastener 4 into the bone. In the illustrated embodiment,the tool engagement surface of the head 16 has a polygonal recess 24.For instance, the polygonal recess 24 may be a torx-shaped recess or ahexagonal recess that receives a hexagonal tool, such as an allenwrench, for example. The present invention is intended to encompass toolengagement surfaces having other shapes as well.

Referring now to FIGS. 1-3, clamp element 7 of the locking clampassembly 6 will be described in more detail in accordance withembodiments of the present invention. As illustrated, the clamp element7 includes a first clamp portion 26 and a second clamp portion 28. Inthe illustrated embodiment, the first clamp portion 26 is substantiallyidentical to and a mirror image of, the second clamp portion 28. Thefirst and second clamp portions 26, 28 provide a collar about the head16 of the bone fastener 4, when installed, as discussed in more detailbelow. The first and second clamp portions 26, 28 grip bone fastener 4when force is applied onto the clamp element 7 by the tulip element 10.While the embodiments that are described and illustrated generallydescribe the first and second clamp portions 26, 28 as substantiallyidentical, the portions 26, 28 may be of varying size and are notrequired to be mirror images of one another. In addition, while theclamp element 7 is illustrated as having two clamp portions (i.e., thefirst and second clamp portions 26, 28), the clamp element 7 maycomprise more than two portions for gripping the bone fastener 4.

As illustrated, each of the first and second clamp portions 26, 28includes an outer surface 30, 32, which may be curved or rounded, asbest shown in FIGS. 1 and 2. The outer surfaces 30, 32 of the first andsecond clamp portions 26, 28 may each include an outer tapered surface34, 36. In addition, the outer surfaces 30, 32 may each also have atleast one slit 38 formed therein. The at least one slit 38 may, forexample, allow the first and second clamp portions 26, 28 to constrictand securely engage the head 16 of the bone fastener 4. The outersurfaces 30, 32 should abut and engage the inner wedge surface 86 of thetulip element 10 of FIG. 6 when fully installed and locked in place inthe tulip element 10 in accordance with present embodiments. Withparticular reference to FIG. 3, the first and second clamp portions 26,28 each include inner surfaces 39, 40. When fully installed and lockedin place in the tulip element 10, the inner surfaces 39, 40 should abutand engage the head 16 of the bone fastener 4 in accordance with presentembodiments. The illustrated embodiment shows the inner surfaces 39, 40having roughened or textured features 42, 44 that improve engagementwith the head 16 of the bone fastener 4. The first and second clampportions 26, 28 each may also include an external lip 46, 48, which maybe located above the outer tapered surfaces 34, 36, as best seen in FIG.3. The first and second clamp portions 26, 28 each may also include anupper surface 31, 33, as best seen in FIG. 1.

Referring now to FIGS. 1-5, the saddle element 8 of the locking clampassembly 6 will be described in more detail in accordance withembodiments of the present invention. As illustrated, the saddle element8 may include a bore 50. The lower portion of the bore 50 may be sizedto receive the upper portion of the clamp element 7, including externallips 46, 48 of the first and second clamp portions 26, 28. The body ofthe saddle element 8 includes an outer surface 52 having a recessedportion 54. The outer surface 52 may be generally rounded, for example.As best seen in FIG. 4, the outer surface 52 of the saddle element 8 maybe generally elliptical, in one embodiment. The elliptical shape of theouter surface 52 should, for example, limit radial motion of the saddleelement when installed in the tulip element 10. The elliptical shape ofthe outer surface 52 should, for example, limit radial motion of thesaddle element 8 when installed in the tulip element 10. The saddleelement 8 further may include an upper surface 56. In the illustratedembodiment, the upper surface 56 defines a seat that receives the rod14. As illustrated, the upper surface 56 may be generally convex inshape. In the illustrated embodiment, the saddle element 8 furtherincludes an upper lip 57.

With particular reference to FIG. 3, the saddle element 8 furtherincludes an inner wedge surface 58. As illustrated, the inner wedgesurface 58 may be disposed around a lower portion of the body of thesaddle element 8. In one embodiment, the inner wedge surface 58 forms aconical wedge. The inner wedge surface 58 operates, for example, toengage the outer tapered surfaces 34, 36 of the first and second clampportions 26, 28 to force the clamp element 7 down the bore 62 of thetulip element 10. The saddle element 8 further may include an innerprotruding surface 60 adjacent to the inner wedge surface 58 and aninner recessed surface 63 adjacent the inner protruding surface 60. Thesaddle element 8 further may include an inner seat 64. As illustrated,the inner seat 64 may be downwardly facing for receiving upper surfaces31, 33 of the first and second clamp portions 26, 28.

In accordance with present embodiments, the locking clamp assembly 6 canbe assembled prior to insertion into the tulip element 10. In oneembodiment, for assembly, the clamp element 7 may be inserted into thesaddle element 8 upwardly through the opening of the body of the saddleelement 8. The outer surfaces 30, 32 of the first and second clampportions 26, 28 should slidingly engage the inner wedge surface 58 ofthe saddle element 8 as the clamp element 7 is inserted. The clampelement 7 should be inserted until the external lips 46, 48 of the firstand second clamp portions 26, 28 pass the inner protruding surface 60 ofthe saddle element 8. The inner protruding surface 60 engages theexternal lips 46, 48 to secure the clamp element 7 in the saddle element8. In the illustrated embodiment, the locking clamp assembly 6 will notfit downwardly through the top of the bore 62 of the tulip element 10 asthe locking clamp assembly has an outer diameter at its biggest pointthat is larger than the inner diameter of the upper portion of the bore62.

Referring now to FIGS. 1 and 6-8, the tulip element 10 will be describedin more detail in accordance with embodiments of the present invention.As illustrated, the tulip element 10 may comprise bore 62, a body 65 anda pair of oppositely positioned lateral arms 66 that extend upwardlyfrom the body 65. In the illustrated embodiment, the arms 66 define aU-shaped channel 68 sized to receive the rod 14. Each of the arms 66 hasan interior surface 70 having a threaded portion 72 for engagingcorresponding threads on a screw-driving tool. The interior surface 70of each of the arms 66 further may include a slot 74 for receivingcorresponding tabs 96 (e.g., FIG. 9) of the locking cap assembly 12 anda recessed surface 76 for engaging corresponding protuberances 100(e.g., FIG. 9) of the locking cap assembly 12. As illustrated, therecessed surface 76 of each of the arms 66 may be located above the slot74. The interior surface 70 of each of the arms 66 further may include aprotuberance 78, as best seen in FIG. 6. In the illustrated embodiment,the protuberance 78 of each of the arms 66 is located below the threadedportion 72 with the threaded portion 72 being located between theprotuberance 78 and the slot 74. As best seen in FIG. 6, the interiorsurface 70 of each of the arms 66 further may form a downwardly facingseat 79, for example, which may limit or restrict movement of thelocking clamp assembly 6 through the bore 62. In some embodiments,saddle element 8 has a pair of oppositely positioned projections, witheach projection extending laterally outwardly from the outer surface 52.Each projection is adapted to be received in a corresponding recessarranged in the interior surface of the tulip element 10. The recess issized and shaped to complement the size and shape of the projections inorder to limit radial motion of the saddle element 8 when installed inthe tulip element. Continuing with the illustrative embodiment of thepresent invention, as each of the arms 66 further may include an outersurface 80. The outer surface 80 of each of the arms 66 may include atool engagement groove 82 formed on the outer surface 80, which may beused for holding the tulip element 10 with a suitable tool (notillustrated).

As illustrated, the body 65 of the tulip element 10 may have an outersurface 84, which may be curved or rounded, as best seen in FIG. 1. Withparticular reference to FIGS. 6 and 7, the body 65 further may includean inner wedge surface 86 disposed around a lower portion of the bore62. In one embodiment, the inner wedge surface 86 forms a conical wedge.The inner wedge surface 86 of the body 65 of the tulip element 10, forexample, may abut and engage the outer surfaces 30, 32 of the first andsecond clamp portions 26, 28 when the locking clamp assembly 6 is fullyinstalled and locked in place.

In accordance with present embodiments, the locking clamp assembly 6 maybe installed in the tulip element 10 in either an unlocked position or alocked position. FIG. 6 illustrates the locking clamp assembly 6disposed in the tulip element 10 in the unlocked position in accordancewith embodiments of the present invention. In FIG. 6, the locking clampassembly 6 has been inserted into the tulip element 10 upwardly throughthe bore 62. The locking assembly 6 should be inserted until the upperlip 57 of the saddle element 8 passes the protuberances 78 located onthe interior surfaces 70 of the arms 66 of the tulip element 10. Theprotuberances 78 should engage the upper lip 57 to secure the lockingclamp assembly 6 in the tulip element 10. While not illustrated on FIG.6, the bone fastener 4 (e.g., shown on FIG. 1) can now be placed intothe locking assembly 6 through a snap fit engagement with the clampelement 7. There should be sufficient clearance for the clamp element 7to expand and snap around the head 16 of the bone fastener 4. Thelocking clamp assembly 6 and the tulip element 10, however, should stillbe free to pivot and rotate with respect to a central axis of the bonefastener 4. The tulip element 10 can be moved and rotated to obtain adesired portion with respect to the bone fastener 4. The locking clampassembly 6 should also move with the tulip element 10 during rotation ofthe tulip element 10 with respect to the bone fastener 4. Once the tulipelement 10 is at the desired position, the tulip element 10 may belocked onto the bone fastener 4. The locking clamp assembly 6 and thetulip element 10 should cooperate to lock the clamp assembly 6 onto thehead 16 of the bone fastener 4.

FIG. 7 illustrates the locking clamp assembly 6 disposed in the tulipelement 10 in the locked position in accordance with embodiments of thepresent invention. In FIG. 7, the locking clamp assembly 6 has beenpushed downwardly in the bore 62 of the tulip element 10. Asillustrated, the locking clamp assembly 6 has been pushed downward untilthe upper lip 57 of the saddle element 8 passes the protuberances 78located on the interior surfaces 70 of the arms 66 of the tulip element10. As the locking clamp assembly 6 moves downward, the clamp element 7engages the body 65 of the tulip element 10. As illustrated, the outersurfaces 30, 32 of the first and second clamp portions 26, 28 of theclamp element 7 should abut and engage the inner wedge surface 86 of thebody 65 of the tulip element 10, forcing inner surfaces 38, 40 of thefirst and second clamp portions 26, 28 to engage head 16 of the bonefastener 4 (e.g., FIG. 1). In the locked position, tulip element 10should be locked onto the bone fastener 4, thus preventing furtherpositioning of the tulip element 10 with respect to the bone fastener 4.

Referring now to FIGS. 1 and 9-11, the locking cap assembly 12 will bedescribed in more detail in accordance with embodiments of the presentinvention. As illustrated, the locking cap assembly 12 may comprise abody 88 and a set screw 90 threaded into a bore 92 in the body 88. Theset screw 90 may have a length, for example, that is longer than thelength of the bore 92. In the illustrated embodiment, at least a portionof the set screw 90 extends from the top of the body 88. In certainembodiments, the set screw 90 may have a tool engagement surface, forexample, that can be engaged by a screw-driving tool or other device.The tool engagement surface can permit the physician to apply torsionalor axial forces to the set screw 90 to advance the set screw 90 throughthe body 88 and onto the rod 14. When the locking cap assembly 12 is inits locked position, the set screw 90 can be advanced through the body88 to engage the rod 14, applying downward force onto the rod 14 andsecuring it to the tulip element 12. In one embodiment, the set screw 90forces the rod 14 downward and into contact with the locking clampassembly 6 causing the locking cap assembly 6 to move downward in thetulip element 10. In the illustrated embodiment, the tool engagementsurface of the set screw 90 is a polygonal recess 94. For instance, thepolygonal recess 94 may be a hexagonal recess that receives a hexagonaltool, such as an allen wrench, for example. The present invention isintended to encompass tool engagement surfaces having other shapes, suchas slot or cross that may be used, for example, with other types ofscrewdrivers. In an alternative embodiment (not illustrated), theengagement surface may be configured with a protruding engagementsurface that may engage with a tool or device having a correspondingrecess.

In accordance with present embodiments, the body 88 may have one or moreprojections. For example, the body 88 may comprise lower tabs 96projecting radially from a lower end of the body 88. In the illustratedembodiment, the body 88 comprises a pair of lower tabs 96 located onopposite sides of the body 88. As illustrated, the lower tabs 96 mayeach have an outer surface 98 that is generally rounded in shape. Inaddition, while the body 88 is illustrated as having two lower tabs 96,the body 88 may comprise more than two lower tabs 96. As illustrated,the body 88 further may comprise protuberances 100. The protuberances100 may engage with corresponding recessed surface 76 of the arms 66 ofthe tulip element 10. The protuberances 100 may be capable of providinga tactile or audible signal to the physician, such as a click that maybe felt or heard, when the locking cap assembly 12 has reached itslocking position. The protuberances 100 also may assist in maintainingthe locking cap assembly 12 in its locked position. In the illustratedembodiment, the body 88 further may comprise tool engagement features.The tool engagement features may, for example, be used for holding ormanipulating the locking cap assembly 12 with a suitable tool (notillustrated). In the illustrated embodiment, the locking cap assembly 12includes upper tabs 102. As illustrated, the tabs 102 may be formed atthe upper surface of the body 88. In the illustrated embodiment, thelocking cap assembly 12 includes four upper tabs 102 at the corners ofthe upper surface. In addition, while the body 88 is illustrated ashaving four upper tabs 102, the body 88 may comprise more or less thanfour upper tabs 102.

To place the locking cap assembly 12 onto the tulip element 10, thelower tabs 96 should be aligned with the U-shaped channel 68 formed bythe arms 66 of tulip element 10 and the locking cap assembly 12 can thenbe lowered downward into the bore 62 in the tulip element 10. Once thelower tabs 96 are aligned with the corresponding slots 74 in the arms 66of the tulip element 10, the locking cap assembly 12 can be rotated. Theslots 74 allow the lower tabs 96 to pass through the arms 66 when thelower tabs 96 and the slots 74 are aligned. The length of the slots 74generally correspond to the amount of rotation needed to move thelocking cap assembly 12 into or out of a locked position. In oneembodiment, the locking cap assembly 12 rotates from about 60° to about120° for placement into a locking positions, alternatively, about 80° toabout 100°, and, alternatively, about 90°. As previously mentioned, theprotuberances 100 can be configured to provide a tactile or audiblesignal to the physician when the locking cap assembly 12 has reached itslocked assembly. In addition, the protuberances 100 can also assist inmaintaining the locking cap assembly 12 in its locked position. Otherfeatures such as undercuts and geometric mating surfaces may be used toprevent rotation in the opposite direction. With the locking capassembly 12 locked in place, the set screw 94 can then be rotated. Asthe set screw 94 moves downward and extends from the bottom of the base88 of the locking cap assembly 12, the set screw 94 presses against therod 14 securing it in the tulip element 10. In addition, the rod 14 mayalso be pressed downward into engagement with the locking clamp assembly6 forcing it downward in the tulip element 10. As the locking clampassembly 6 moves downward, the clamp element 7 engages the body 65 ofthe tulip element 10. As best seen in FIG. 7, the outer surfaces 30, 32of the first and second clamp portions 26, 28 of the clamp element 7should abut and engage the inner wedge surface 86 of the body 65 of thetulip element 10, forcing inner surfaces 38, 40 of the first and secondclamp portions 26, 28 to engage head 16 of the bone fastener 4 andsecure it with respect to the tulip element 10.

Referring now to FIGS. 12-14, locking of the tulip element 10 onto thebone fastener 4 is illustrated in more detail in accordance withembodiments of the present invention. For the purposes of thisillustration, the locking cap element 12 is not shown. The tulip element10 shown in FIGS. 12-14 is similar to the tulip element 10 describedpreviously except that the tulip element 10 does not include a threadedportion 72 (e.g., FIGS. 6-7) or a downwardly facing seat 79 (e.g., FIG.6) in the interior surface 70 of the arms 66 of the tulip element 10.FIG. 12 illustrates the locking clamp assembly 6 installed in the tulipelement 10 in an unlocked position. As previously mentioned, the lockingclamp assembly 6 can be inserted into the tulip element 10 upwardlythrough the bore 62. As shown in FIG. 12, the locking assembly 6 shouldbe inserted until the upper lip 57 of the saddle element 8 passes theprotuberances 78 located on the interior surfaces 70 of the tulipelement 10. The protuberances 78 should engage the upper lip 57 tosecure the locking clamp assembly 6 in the tulip element 10. Asillustrated by FIG. 13, the bone fastener 4 can now be placed into thelocking assembly 6 through a snap fit with the clamp element 7. Thereshould be sufficient clearance for the clamp element 7 to expand andsnap around the head 16 of the bone fastener 4. The locking clampassembly 6 and the tulip element 10, however, should still be free topivot and rotate with respect to the bone fastener 4. The tulip element10 can be pivoted and rotated to obtain a desired portion with respectto the bone fastener 4. Once the tulip element 10 is at the desiredposition, the tulip element 10 may be locked onto the bone fastener 4.The locking clamp assembly 6 and the tulip element 10 should cooperateto lock the clamp assembly 6 onto the head 16 of the bone fastener 4.

FIG. 14 illustrates the locking clamp assembly 6 disposed in the tulipelement 10 in the locked position and clamping onto the head 16 of thebone fastener 4 to secure the bone fastener 4 with respect to the tulipelement 10 in accordance with embodiments of the present invention. Asseen in FIG. 14, the locking clamp assembly 6 has been pushed downwardlyin the bore 62 of the tulip element 10 until the upper lip 57 of thesaddle element 8 passes the protuberances 78 located on the interiorsurfaces 70 of the arms 66 of the tulip element 10. As the locking clampassembly 6 moves downward, the clamp element 7 engages the body 65 ofthe tulip element 10 such that the outer surfaces 30, 32 of the firstand second clamp portions 26, 28 of the clamp element 7 should abut andengage the inner wedge surface 86 of the body 65 of the tulip element10, forcing inner surfaces 38, 40 of the first and second clamp portions26, 28 to engage head 16 of the bone fastener 4. In the locked position,tulip element 10 should be locked onto the bone fastener 4, thuspreventing further positioning of the tulip element 10 with respect tothe bone fastener 4.

During a surgical procedure, the polyaxial tulip assembly 101 is coupledto the polyaxial head 16 of the bone fastener 4, as shown in FIG. 12.With a driving tool, the surgeon can insert the bone fastener 4 (withthe tulip assembly 101 coupled to the head 16) into a pedicle orvertebral body located at a particular region of a spinal column.However, as discussed at the beginning of this disclosure, the surgeonmay intra-operatively determine after the bone fastener 4 has beeninserted into the pedicle or vertebral body that deformity correction isneeded at this particular region of the spinal column.

In accordance with the illustrative embodiment, the surgeon canuncouple, detach, etc., the polyaxial tulip assembly 101 from the bonefastener head 16 and then couple, install, etc., the uniplanar tulipassembly 551 onto the same bone fastener head 16. As will be appreciatedfrom the description below, the adapter 502 when used in conjunctionwith the uniplanar tulip assembly 551 will allow it to pivot or angulatein a single plane relative to the polyaxial bone fastener head 16, whilesimultaneously preventing movement of the tulip assembly 551 in allother directions and planes of the bone fastener head 16. These featuresof the present invention will be described in more detail below, withrespect to FIGS. 15-18D.

FIG. 15 depicts a uniplanar tulip assembly 551, which includes tulipelement 553 and locking clamp assembly 559 (i.e., clamp element 557 andsaddle element 555). It will be clear to those skilled in the art, afterreading this disclosure, that the tulip element 553 and the lockingclamp assembly 559 are coupled or assembled together in the same orsimilar fashion as the polyaxial tulip assembly 101 and locking clampassembly 6 discussed above, with respect to FIGS. 1-14. One difference,however, is that the uniplanar saddle element 555 has a longitudinalslot 561 and a pair of oppositely positioned lateral protrusions 550,each of which is not present in the polyaxial saddle element 8. Each ofthe lateral protrusions 550 of the uniplanar saddle elements 555 issized and shaped to be received in a corresponding recess 563 arrangedon an inner surface of the tulip element 553. Once received, saddleelement 555 is prevented from rotating within the tulip element 553. Itshould also be noted that the uniplanar tulip assembly 551 is adapted tobe coupled, installed, etc., onto the bone fastener head 16 in the sameor similar fashion as the polyaxial tulip assembly 101 discussed above,with respect to FIGS. 1-14.

FIG. 15 further depicts two adapters 502, with each adapter having adifferent shaped lower portion 504. The combination of the tulipassembly 551 and the adaptor 502 form a modular uniplanar pedicle screwassembly 575 in accordance with the present invention. As shown in thefigure, the adapter 502 has a lower portion 504 and an upper portion 506formed as a single, unitary construction. In alternative embodiments,the lower and upper portions can be two separate parts that are coupledtogether to form the adapter 502. In accordance with the illustrativeembodiment, the lower portion 504 of the adapter 502 is sized and shapedto be received in the recess 24 of the polyaxial bone fastener head 16.In one embodiment, the lower portion 504 has a shape that complementsthe shape of recess 24, in order to prevent the adaptor 502 from beingable to rotate about a central axis of the bone fastener head 16. Thiscomplementary shape of the lower portion and recess is shown in FIG. 16.The lower portion 504 and recess 24 can have any shape (e.g.,torx-shaped, hexagonal-shaped, polygonal-shaped, etc.), as long as theshape is able to prevent the lower portion 504 from being able to rotatein the recess 24. As will be described in more detail below, combiningthis physical relationship with that of the upper portion 506 and thelongitudinal slot 561 will enable the uniplanar tulip assembly 551 topivot in a single plane, while simultaneously preventing movement of thetulip assembly 551 in all other directions and planes of the bonefastener 4.

Returning back to FIG. 15, this figure further illustrates the upperportion 506 of the adapter 502 extending from the lower portion 504. Theupper portion 506 is defined by an upper surface 508 having a recess orhole 510, a pair of oppositely positioned lateral surfaces 512, and apair of oppositely positioned inclined surfaces 514. Although FIG. 15only depicts one lateral surface and one inclined surface, it should benoted that one half of the adapter 502 (when divided into equal halves)is substantially identical to and a mirror image of the other half ofadapter 502. Continuing with FIG. 15, it is shown that each of theoppositely positioned inclined surfaces 514 form a flange 516, with eachflange having an underside that will rests on top of the polyaxial bonefastener head 16.

To allow the uniplanar tulip assembly 551 to pivot or angulate about thepolyaxial bone fastener head 16, the upper portion 506 is adapted to bereceived in the longitudinal slot 561 of the saddle element 555. Asshown in FIG. 17A, the width of the upper portion 506 is slightlysmaller than the width of the longitudinal slot 561 of the saddleelement 555. That is, the upper portion 506 is sized and shaped in sucha way that each of the lateral surfaces 512 of the adapter abuts againstrespective oppositely positioned inner walls 518 of the longitudinalslot 561. This prevents the uniplanar tulip assembly 551 from pivotingor angulating in a direction and plane that is perpendicular to thelongitudinal slot 561. As further shown in FIG. 17A, the upper portion506 once inserted into the longitudinal slot 561 does not extend pastthe upper surface of the pair of oppositely positioned inner walls 518of the longitudinal slot 561. In alternative embodiments, however, theupper portion 506 may extend past the upper surface of the pair ofoppositely positioned inner walls 518. Although FIG. 15 only depicts oneinner wall 518, it will be appreciated by those skilled in the art thatone half of the saddle element 555 (when divided into equal halves) issubstantially identical to and a mirror image of the other half of thesaddle element.

From the physical relationship of the elements discussed above, theupper portion 506 is adapted to slide along the longitudinal slot 561 ofthe uniplanar tulip assembly 551 (i.e., along the longitudinal slot ofthe saddle element 555 and in the direction of the arrows illustrated inFIGS. 17B and 17C) to allow movement of the tulip assembly 551 (whichincludes the tulip element 553, clamp element 557, and saddle element555) in a first plane along a direction that is parallel to alongitudinal axis of the longitudinal slot 561. When sliding along thelongitudinal slot, the pair of oppositely positioned inclined surfaces514 abut against respective oppositely positioned inner walls 520 of thetulip assembly 551 (e.g., the inner wall of the clamp element 557,saddle element 555, or combination thereof) to stop the upper portion506 from sliding past a predefined location along the longitudinal slot561. The physical relationship of the lower and upper portions alsoprevents any sort of pivoting or angular movement of the uniplanar tulipassembly 551 in a second plane lateral to the first plane relative tothe bone fastener 4, thereby providing rigidity in the second plane sothat a surgeon can adjust (e.g., straighten-out, undeform, etc.) aparticular region of a patient's spinal column that is suffering fromscoliosis or other spinal deformities.

In accordance with the illustrative embodiment, the direction parallelto the longitudinal axis of the longitudinal slot 561 in the first planeis the cephalad-caudal direction of a body (i.e., the direction fromhead to toe), while the second plane lateral to the first plane is themedial-lateral direction of the body (i.e., the direction from themidline of the body to the side).

As discussed above, alternative embodiments of the present inventionenable the adapter 502 to rotate about a central axis of the polyaxialbone fastener head 16 to change the plane in which the uniplanar tulipassembly 551 can pivot or angulate. To achieve this, the lower portion504 has a cylindrical shape, instead of a shape that prevents the lowerportion 504 from rotating while in the recess 24, as discussed above.The cylindrical shape of the lower portion 504 is shown in FIG. 15. Whenthe cylindrical lower portion 504 is used in combination with the upperportion 506, this combination enables the uniplanar tulip assembly 551(even when clamped onto the bone fastener head 16) to rotate about acentral axis of the head 16. In this way, the surgeon canintra-operatively change the plane in which the tulip assembly 551pivots or angulates.

For example, the uniplanar tulip assembly 551 including the adapter 502is clamped onto the polyaxial bone fastener head 16. The surgeon wouldlike to intra-operatively change the pivot or angulation plane of thetulip assembly 551 from the cephalad-caudal section to themedial-lateral section of the body. The surgeon can achieve this byrotating the tulip assembly 90° while the tulip assembly 551 is clampedonto the bone fastener head 16. Because the upper portion 512 of theadapter 502 is arranged within the tulip assembly 551 in the mannerdiscussed above, rotating the tulip assembly 90° will also rotate theadapter 90°. Once rotated, the uniplanar tulip assembly 551 can nowpivot or angulate about a central axis of the polyaxial bone faster head16 in the medial-lateral direction, while preventing movement in thecephalad-caudal direction.

It should be clear to those skilled in the art, after reading thisdisclosure, that the tulip assembly 551 (when employing the adapter 502with a cylindrical lower portion 504) can be rotated in any number ofdegrees to change the direction/plane in which the tulip assembly 551may pivot and prevent movement. In alternative embodiments of thepresent invention, the longitudinal slot 561 may be orientedperpendicular to the orientation shown in the illustrative embodiment,or at another angle. This alternative orientation allows the uniplanartulip assembly 551 to angle in, for example, and without limitation, themedial-lateral direction while maintaining rigidity in thecephalad-caudal direction of a body.

The present invention also provides an insertion tool 600 that comprisesa spring-loaded, self-retaining tip 602. FIG. 18A-18D respectivelyillustrate: (i) loading the adapter 502, (ii) inserting the adapter 502into the recess 24 of the polyaxial bone fastener head 16, (iii)releasing the adapter 502 and coupling the uniplanar tulip assembly 551onto the bone fastener head 16, and (iv) the misalignment of the adapter502 during the insertion step.

As shown these figures, the self-retaining tip is sized and shaped to beinserted into a hole 510 of the adapter 502. As a surgeon inserts theself-retaining tip 602 into an upper hole 530 of the hole 510, theself-retaining tip will retract upwards into the housing of theinsertion tool 600, as shown in FIG. 18A. To prevent the self-retainingtip 602 from retracting too far up into the housing, a knob 608 isprovided. The knob is adapted to restrict an internal pin 604 fromtraversing a return channel 606. Once the adapter 502 has been loadedinto the insertion tool 600, along with the uniplanar tulip assembly551, the surgeon can remove the knob 608 from the insertion tool 600.

Once the knob 608 is removed from the insertion tool 600, the surgeonaligns the lower portion 504 of the adapter 502 with the recess 24 ofthe polyaxial bone fastener head 16, as shown in FIG. 18B. The pin 604will traverse the return channel 606 as the lower portion 504 of theadapter abuts against the bottom of recess 24 (aligned) or the outersurface of the bone fastener head 16 (misaligned). As the pin 604traverses the return channel 606, it simultaneously moves a blockingmechanism 610 from left to right, as shown in FIG. 18C. During thisstage, the surgeon will be listening for a sound or physical feedbackfrom the uniplanar tulip assembly 551. These indications signify thatthe lower portion 504 of the adapter 502 has been properly aligned andseated within the recess 24. More specifically, the sound or physicalfeedback is an indication that the tulip assembly 551 is now seated inthe bone fastener head 16 and the blocking mechanism 610 has reached apredefined location within insertion tool 600 (as shown in FIG. 18C), atwhich point the surgeon can engage a handle on the insertion tool 600 sothat the tulip assembly 551 can be clamped (via the locking clampassembly 559) onto the polyaxial bone fastener head 16. However, if thelower portion 504 of the adapter 502 is misaligned with the recess 24,the pin 604 will traverse too far along the return channel 606, therebycausing the blocking mechanism 610 to continue blocking the handle frombeing able to be operated by the surgeon (as shown in FIG. 18D).

In alternative embodiments, a surgeon can simply insert the lowerportion 504 of the adapter 502 into the recess 24 of the polyaxial bonefastener head 16. In this alternative embodiment, the self-retaining tip602 of the insertion tool 600 will be inserted into the upper hole 530while the lower portion 504 of the adapter 502 is seated in the recess24. When the tip 602 is aligned with the upper hole 530 and has beensuccessfully inserted into the upper hole, the blocking mechanism 610will move to a particular position within the insertion tool 600, asshown in FIG. 18C. It should be noted that the upper portion 506 of theadapter 502 is also inserted into the longitudinal slot 561 when the tip602 has been successfully inserted into the upper hole 530. At thispoint, the surgeon can engage a handle on the insertion tool 600 toclamp the tulip assembly 551 onto the bone fastener head 16, asdiscussed above. If the tip 602 is misaligned with the upper hole 530,the pin 604 will traverse too far along the return channel 606, therebycausing the blocking mechanism 610 to continue blocking the handle frombeing able to be operated by the surgeon (as shown in FIG. 18D).

A method of using the modular uniplanar pedicle screw assembly 575 on apolyaxial bone fastener 4 that has been inserted into a vertebrae willnow be described. The bone faster 4, with the polyaxial tulip assembly101 coupled thereto, is inserted into a vertebrae. At some point duringthe surgery, the surgeon may determine intra-operatively that deformitycorrection is needed at the affected vertebral body and that a uniplanarassembly would be more suitable for this purpose. In accordance with theillustrative embodiment of the present invention, the surgeon can use aspecialized tool to decouple the polyaxial tulip assembly 101 from thepolyaxial bone fastener 4; in particular, the bone fastener head 16.Once the polyaxial tulip assembly 101 has been decoupled, the surgeonmay inserting the lower portion 504 of the adapter 502 into the recess24 arranged on the head 16 of the polyaxial bone fastener 4. Similarly,the upper portion 506 of the adapter 502 is inserted into thelongitudinal slot 561 of the uniplanar tulip assembly 551, as discussedabove with respect to FIGS. 18A-18C. The upper portion 506 is adapted toslide along the longitudinal slot 561 to allow movement of the uniplanartulip assembly 551 in a first plane along a direction that is parallelto a longitudinal axis of the longitudinal slot, while preventingmovement of the uniplanar tulip assembly 551 in a second plane lateralto the first plane relative to the bone fastener 4. Once the upper andlower portions of the adapter have inserted, and the uniplanar tulipassembly 551 has been coupled onto the bone fastener head 16, thesurgeon attaches a fusion bar to the uniplanar tulip assembly. Morespecifically, the surgeon may seat the fusion bar 14 on the U-shapedchannel 68 of the saddle element 555. A locking cap 12, for example, isthreaded onto the uniplanar tulip assembly 575 to lock it onto the bonefastener head 16. Thereafter, the surgeon may move the affectedvertebrae to a desired position in the second plane using the uniplanartulip assembly 575 with the inserted adapter 502 and the attached fusionbar 14.

A Modular Uniplanar Tulip Assembly Having a Pivoting Saddle Element

FIG. 19A is a perspective view of a uniplanar tulip assembly 700 inaccordance with an alternative embodiment of the present invention.FIGS. 19B and 19C respectively show side and front cross-sectional viewsof the tulip assembly 700. FIG. 20 depicts the elements that form thetulip assembly 700.

FIGS. 19A-19C show the uniplanar tulip assembly 700 having a tulipelement 702 and a locking clamp assembly 704 (which comprises the clampelement 706 and the saddle element 708 depicted in FIG. 20). The lockingclamp assembly 704 can be assembled and installed into the tulip element702 in the same or similar fashion as the locking clamp assembly 6discussed above, with respect to FIGS. 1-14. Although not shown in FIGS.19A-19C, the polyaxial pedicle screw assembly 700 also comprises a bonefastener and a locking cap assembly, each of which can be the same as ordifferent than the bone fastener 4 and locking cap assembly 12 discussedabove.

In general, the tulip assembly 700 is similar to the tulip assembly 101depicted in FIG. 1, with the exception that the saddle element 708 maynot have a longitudinal slot 561 for receiving an adapter 502. Instead,to be able to use the uniplanar tulip assembly 700 with the polyaxialbone fastener 4, the inner surface 710 of each oppositely positionedlateral arm 712 of the tulip element 702 is arranged with a recess 714(e.g., keyhole, etc.) that is adapted to receive a correspondingprotrusion 716 of the saddle element 708.

More specifically, FIG. 19B depicts the clamp element 706 and the saddleelement 708 assembled to form the locking clamp assembly 704. The clampelement 706 includes at least one slit 738 that divides the clampelement into a first clamp portion 726 and a second clamp portion 728.The at least one slit 738 may, for example, allow the first and secondclamp portions 726, 728 to constrict and securely engage the head 16 ofthe bone fastener 4. FIG. 19B, however, depicts the tulip element 702 inan unlocked position (e.g., as discussed above with respect to FIG. 6).In the unlocked position, the tulip element 702, clamp element 706, andsaddle element 708 are allowed to, as a single unit, rotate about acentral axis (i.e., the rotation axis 746 of FIG. 19C) of the bonefastener 4 and pivot/angulate freely about the bone fastener head 16.

At some point in time, the surgeon may cause the first and second clampportions 726, 728 to constrict and engage the head 16 of the bonefastener 4, thereby placing the clamp element 706 and the saddle element708 in a locked position (e.g., as discussed above with respect to FIG.7). In the locked position, the tulip element 702, clamp element 706,and saddle element 708 can no longer rotate about the central axis ofthe bone fastener 4. The locked position further disallows the clampelement 706 and the saddle element 708 from pivoting/angulating in anyand all planes of the bone fastener head 16. The only element that isallowed to pivot/angulate in the locked position is the tulip element702, which element is only allowed to pivot/angulate in a single planeof the polyaxial bone fastener head 16. That is, since each of theoppositely positioned lateral protrusions 716 of the saddle element 708is sized and shaped to be received in a respective recess 714 arrangedon the inner surface 710 of the tulip element 702, the tulip element 702is allowed to pivot/angulate along the articulating plane 744 depictedin FIG. 19C. The articulating plane can be, for example, and withoutlimitation, the medial-lateral direction or the cephalad-caudaldirection of a body. When the surgeon wishes to re-adjust thepivoting/angulation plane of the tulip element 702, the surgeon mayplace the tulip assembly in the unlocked position using a tool andrepeat the steps above.

By employing this configuration, a surgeon can have the flexibility ofpolyaxial angulation of a pedicle screw and the ability to independentlylock the screw into uniplanar or bi-planar angulation to providerigidity in a particular plane.

A Tulip Sleeve for Converting a Polyaxial Pedicle Screw to a UniplanarPedicle Screw

FIG. 21 is a perspective view of a polyaxial pedicle screw that can beconverted to a uniplanar pedicle screw using a sleeve assembly 800 inaccordance with an alternative embodiment of the present invention.

In this alternative embodiment of the present invention, the tulipelements 10, 702 can be modified to receive a sleeve assembly 800 forpreventing the tulip assembly from pivoting or angulating in aparticular plane of the bone fastener head 16. As shown in FIG. 22,tulip element 802 (which can have substantially the same or differentstructural, physical, and/or functional characteristics as tulipelements 10, 702 discussed above) comprises a recess 804 that isarranged at a lower portion of the outer surface 806 of a lateral arm808. It will be clear to those skilled in the art, after reading thisdisclosure, that the other lateral arm 810 is substantially identical toand a mirror image of the lateral arm 808. The recess 804 of eachlateral arm 808, 810 is sized and shaped to receive and complement acorresponding insert 816 for attaching the sleeve assembly 800 to thetulip element 802. The inserts 816 fit squarely into the recesses 804 toprovide the functionality of preventing the sleeve assembly 800 fromaxial and rotational movement relative to the tulip element 802.

As shown in FIG. 23, the sleeve assembly 800 is constructed and arrangedwith a first portion 812 and a second portion 814. The portions arejoined together to form the sleeve assembly 800 depicted in the figure.Each of the first and second portions 812, 814 include a pin 818. Whenthe sleeve assembly 800 is attached to the tulip element 802 via theinserts 816, the bottom surface of the bone fastener head 16 rests ontop of the pins 818, while the shaft 18 of the bone fastener 4 comesinto secure engagement with the inwardly protruding pins 818. Thissecure engagement between the pins 818 and the shaft 18 prevents thetulip element 802 from pivoting in the medial-lateral section of a body,while allowing pivoting of the tulip element 802 in the cephalad-caudalsection of the body.

Uniplanar Pedicle Screw Assembly Having Rotational and TranslationalCapabilities

FIG. 24A is a perspective view of a uniplanar pedicle screw assembly 900that allows a bone fastener 4 to have: (i) rotational movement (e.g.,pivoting or angulate) in a first plane along a direction that isperpendicular to a longitudinal axis of a translation rod and (ii)translational movement in a second plane along a direction that isparallel to the longitudinal axis of the translation rod.

FIG. 24B depicts the uniplanar pedicle screw assembly 900 of FIG. 24Adisassembled. As shown in the figure, the assembly 900 comprises a tulipelement 904 having a body 906 and a pair of oppositely positionedlateral arms 908. Tulip element 904 can be substantially the same as ordifferent than the tulip elements discussed above. In this embodiment ofthe present invention, each arm 908 includes a slot 910 (only one isshown in the figure) that is sized and shaped to receive and complementa corresponding saddle retainer 912. Further, each lateral surface ofthe body 906 includes a through-hole 914 (only one is shown in thefigure) that is sized and shaped to receive and complement a translationrod 916 for allowing the bone fastener 4 to have rotational andtranslational capabilities. It will be clear to those skilled in theart, after reading this disclosure, that one half of the tulip element904 is substantially identical to and a mirror image of the other halfof the tulip element. It will also be clear to those skilled in the artthat tulip element 904 can have substantially the same or differentstructural, physical, and/or functional characteristics as tulipelements 10, 702 discussed above. FIG. 24B further depicts a saddleelement 902 and a bone fastener 4 having a head 16 arranged with a pairof oppositely positioned through-holes 918 (only one is shown in thefigure) that is sized and shaped to receive and complement a translationrod 916. In this embodiment of the invention, the pair of oppositelypositioned through-holes 918 of the bone faster head has a similarfunctionality as a yoke. It will be clear to those skilled in the art,after reading this disclosure, that one half of the bone fastener head16 is substantially identical to and a mirror image of the other half ofthe bone fastener head.

FIG. 25A is a front view of the uniplanar pedicle screw assembly 900 ofthe present invention. FIG. 25B is a cross-sectional view of theuniplanar pedicle screw assembly 900 of FIG. 25A. As shown in thefigure, each of the slots 910 is sized and shaped to receive a saddleretainer 912. The upper and lower surfaces of the saddle retainer 912come into secure engagement with the corresponding surfaces of the slot910 when inserted therein. Each of the saddle retainers 912 extendbeyond the upper and lower surfaces of their respective slot 910 inorder to engage an upper lip 926 of the saddle element 902. Thisconfiguration retains the saddle element 902 within the bore 920 of thetulip element 904. Also shown in FIG. 25B is the bone fastener 4 coupledto the tulip element 904 via the translation rod 916. Each of thethrough-holes 918 arranged on the bone fastener head 16 is aligned withtheir respective through-hole 914 arranged on the tulip element 904.Once aligned, the translation rod 916 is inserted through thethrough-holes 914, 918. The ends of the translation rod 916 are peenedto ensure that the rod does not fall out of the through-holes. It shouldbe noted at this point of the disclosure that there is a small gap 934between the bone fastener head 16 and the saddle element 902. As will bedescribed in more detail below, this small gap 934 provides clearance toallow the tulip element 904 to pivot or angulate in a particular plane.

FIG. 26A is a side view of the uniplanar pedicle screw assembly 900 ofthe present invention. FIG. 26B is a cross-sectional view of theuniplanar pedicle screw assembly 900 of FIG. 26A. As shown in thefigure, the saddle element 902 is arranged with a pair of oppositelypositioned teeth 922, each of which is adapted to engage an uppersurface of the bone fastener head 16 to restrict rotational movement ofthe tulip element 904 (relative to a central axis of the bone fastener4) to a predefined range. As further shown in the figure, thetranslation rod 916 enables the tulip element 916 to have rotationalmovement (e.g., pivoting or angulate) in a first plane along a directionthat is perpendicular to a longitudinal axis of the translation rod 916.The rotational movement is made possible by the small gap 934, whichprovides clearance between the saddle element 902 and the bone fastenerhead 16.

FIG. 27A is top view of the uniplanar pedicle screw assembly 900 of thepresent invention, with the top view showing translational movement ofthe tulip element 904 towards the arrow 950. FIG. 27B is a front view ofthe translated uniplanar pedicle screw assembly 900 of FIG. 27B. Asshown in the figures, not only does the translation rod 916 enable thetulip element 904 to pivot or angulate, it also enables the tulipelement 904 to have translational movement in a second plane along adirection that is parallel to the longitudinal axis of the translationrod 916.

Once the tulip element 904 has been rotated or translated to a desiredposition, a locking mechanism is used to secure the tulip element 904 inthat position. As shown in FIG. 28, a fusion rod 14 is seated on anupper surface of the saddle element 902 and a locking cap 924 isthreaded onto the pair of oppositely positioned lateral arms 908 of thetulip element 904. The bottom surface of the locking cap 924 abutsagainst the fusion rod 14, which in turn causes the saddle element 902to constrain movement of tulip element 904 relative to the bone fastenerhead 16.

It is to be understood that the disclosure describes a few embodimentsand that many variations of the invention can easily be devised by thoseskilled in the art after reading this disclosure and that the scope ofthe present invention is to be determined by the following claims.

What is claimed is:
 1. A modular uniplanar pedicle screw assembly foruse with a polyaxial bone fastener, the modular uniplanar pedicle screwassembly comprising: a uniplanar tulip assembly adapted to be coupled toa head of the bone fastener, wherein the uniplanar tulip assemblyincludes a longitudinal slot; and an adapter including: (i) a lowerportion sized and shaped to be received in a recess of the bone fastenerhead, and (ii) an upper portion extending from the lower portion andadapted to slide along the longitudinal slot of the uniplanar tulipassembly to allow movement of the uniplanar tulip assembly in a firstplane along a direction that is parallel to a longitudinal axis of thelongitudinal slot, the longitudinal slot preventing movement of theuniplanar tulip assembly in a second plane lateral to the first planerelative to the bone fastener.
 2. The modular uniplanar pedicle screwassembly of claim 1, wherein the upper portion has a pair of oppositelypositioned lateral surfaces that abut against respective oppositelypositioned inner walls of the longitudinal slot to prevent movement ofthe uniplanar tulip assembly in the second plane.
 3. The modularuniplanar pedicle screw assembly of claim 1, wherein the upper portionhas a pair of oppositely positioned inclined surfaces that abut againstrespective oppositely positioned inner walls of the uniplanar tulipassembly to stop the upper portion from sliding past a predefinedlocation along the longitudinal slot.
 4. The modular uniplanar pediclescrew assembly of claim 1, wherein the upper portion has a pair ofoppositely positioned flanges, each having an underside that rests on anupper surface of the bone fastener head.
 5. The modular uniplanarpedicle screw assembly of claim 1, wherein the lower portion is shapedto complement the shape of the recess to prevent the adaptor fromrotating about a central axis of the bone fastener head.
 6. The modularuniplanar pedicle screw assembly of claim 5, wherein the lower portionis torx-shaped.
 7. The modular uniplanar pedicle screw assembly of claim1, wherein lower portion has a cylindrical shape to allow the adapter torotate about a central axis of the bone fastener head.
 8. The modularuniplanar pedicle screw assembly claim 1, wherein the adapter has a holefor receiving a self-retaining tip of an insertion tool.
 9. The modularuniplanar pedicle screw assembly of claim 8, wherein the hole includes athrough-hole having an upper hole for receiving the self-retaining tipand a lower hole whose diameter is smaller than the upper hole.
 10. Themodular uniplanar pedicle screw assembly of claim 1, wherein the bonefastener head is also adapted to be coupled to a polyaxial tulipassembly, wherein the polyaxial tulip assembly is adapted to polyaxiallymove about a central axis of the bone fastener head.
 11. A method ofusing a modular uniplanar pedicle screw assembly on a polyaxial bonefastener that has been inserted into a vertebrae, the method comprising:inserting a lower portion of an adapter into a recess arranged on a headof the bone fastener; inserting an upper portion of the adapter into alongitudinal slot of a uniplanar tulip assembly, wherein the upperportion is adapted to slide along the longitudinal slot to allowmovement of the uniplanar tulip assembly in a first plane along adirection that is parallel to a longitudinal axis of the longitudinalslot, and wherein the longitudinal slot prevents movement of theuniplanar tulip assembly in a second plane lateral to the first planerelative to the bone fastener; attaching a fusion bar to the uniplanartulip assembly; and moving the vertebrae to a desired position in thesecond plane using the uniplanar tulip assembly with the insertedadapter and the attached fusion bar.
 12. The method of claim 11, whereinthe uniplanar tulip assembly is prevented from rotational ortranslational movement in the second plane as a result of a pair ofoppositely positioned lateral surfaces of the upper portion abuttingagainst respective oppositely positioned inner walls of the longitudinalslot.
 13. The method of claim 11, wherein the upper portion is preventedfrom sliding past a predefined location along the longitudinal slot as aresult of a pair of oppositely positioned inclined surfaces that abutagainst respective oppositely positioned inner walls of the uniplanartulip assembly.
 14. The method of claim 11, wherein the step ofproviding the adapter includes: loading the adapter into an insertiontool by inserting a self-retaining tip of the insertion tool into a holeof the adapter, wherein the hole includes a through-hole having an upperhole for receiving the self-retaining tip and a lower hole whosediameter is smaller than the upper hole.
 15. The method of claim 14,wherein the step of inserting the lower portion into the recessincludes: aligning the lower portion of the adapter with the recessafter the adapter is loaded into the insertion tool; and engaging ahandle of the insertion tool when the lower portion is aligned with therecess so as to insert the lower portion into the recess and to couplethe uniplanar tulip assembly to the bone fastener head.
 16. The methodof claim 11, wherein the uniplanar tulip assembly is coupled to aninsertion tool while the upper portion is being inserted into thelongitudinal slot.
 17. The method of claim 11 further comprising:decoupling a polyaxial tulip assembly from the inserted bone fastener.